Cold-spun articles



Dec. 25, 1956 F. K. BLOOM ET AL 2,775,519

COLD-SPUN ARTICLES Filed Nov. 5, i951 amao/v UP r0 0. ma;

MANGANESE up r0 lsz c/moM/z/M /oz 70 252' NICKEL 7:; T0 202 cop/=5? /.0z m 6.02

INVENTORS 3 FREDRICK K. BLOOM w. LIAM c. CLARKE, JR.

THE/R ATTORNEY IRON REM/Nose 2,775,519 Patented Dec. 25, 1956 2 a ms, -12

, Our invention relates to the production of cold-spun austenitic stainless steel articles displaying reduced workhardening properties, together with such degree of ductility and reduced ultimate tensile strength as to permit considerable cold-working in the substantial absence of necessity for intermediate anneal.

An object of our invention is to produce austenitic stainless steel cold-spun articles by cold-working practices, with importantly reduced work-hardening and with substantial absence of necessity for intermediate anneal,

which products are coldaworked with high rapidity, with x minimum investment in both plant and labor and in highly practical manner. v

Another object is to fabricate cold-spun articles from austenitic stainless steels with substantial reduction in the energy'and powerrequirements and with minimum wear on the cold-forming equipment employed, which articles respond to required high degree of variation in surfaceconfig uration and dimensions, display pleasing surface appearance and lustre, and demonstrate substantial resistance tov corrosion.

Yet another object is to provide cold-spun articles with a minimum number of procedural and manipulative steps, cold-spinning fromstainless steel stock a variety of articles of widely varying surface dimensions and characteristics. l

All these, as well as many other highly practical objects and advantages, attend upon the practice of our invention.

Accordingly, our invention may be seen to reside in the composition of ingredients, features of working and the relation between the same, the scope of the application of all of which is more fully set forth in the claims at the end of this, specification. I

In the single view of the drawings we disclose, by illustration, an ice-bowl produced according to the practice of our invention.

As conducive to a more thorough understanding of certain features of our; invention it may be noted at this point that the widespread use of austenitic chromiumnickel stainless. steels. has become more and more accepted in the productionllof a wide variety of articles of varied description and uses,.a phenomenom largely due to the many. advantageous characteristics of those metals,

markedly superior to those of known metals hitherto used. Among those advantages may be listed the ability to respondltO. high Surface detail and finish with close adherence to limited dimensional tolerances, pleasing surface appearance, inherent resistance to corrosion, and the like at reasonable cost.

Unfortunately, however, there is one marked practical limitation upon the usage of the austenitic chromiumnickel steels; This restriction is due largely to the high rate of work hardening displayed by these metals. Initially much softer than the plain carbon steels or even the straight chromium steels, the chrome-nickel alloys are found, within the'normal range of alloying ingredi- United States Patent Otfice cuts, to harden much more rapidly when subjected to cold-spinning operations, than do these known steels. Expressed in other words, much more energy or power is required to bring about cold deformation as this cold deformation progresses. Moreover, the high loads developed in cold-spinning these metals tend rapidly to wear out the forming equipment employed.

For example, it is known that with alloys possessing reduced nickel content, important and detrimental workha'rdening properties are encountered, materially reducing the use thereof. This tendency towards work-hardening, it is true, can be partly alleviated by increasing either the nickel content or the chromium content. A possible explanation of this is that increase in either of these ingredients in the low alloy steels tends to increase the stability of the chrome-nickel austenite. Conversely, however, it is found that given an initial high proportion of nickel, then upon increase in the chromium content, the work-hardening properties of the alloy are increased, a phenomenon perhaps due to the formation of an extremely hard solid solution of chromium and nickel within the metal. And with the chromium and nickel within the ranges of the typical 18.-8 chromium-nickel stainless steel, an increase in the nickel content is accompanied by a resulting decrease in the work-hardeningrate.

While some relief is afforded, and some decrease in work-hardening rate is observed, by increasing either the nickel or manganese content of the known stainless steel alloysof composition within the usual range, this comprises but a partial solution to the problem. It may be noted in passing that according to this practice, a certain amount ofthe nickel can be used in the replacement or substitution of the manganese, while similarly and con versely, a certain amount of the manganese can be used in substitution for and replacement of the nickel. Thus, it is current practice to increase the nickel content of the conventional 18..8 chromium-nickel alloy byabout 3% to say 18-.11 chromium-nickel, resulting in a more stable austenitic alloy which can be subjected to a certain amount of cold-spinning.

Actually, however, no really practical way has been evolved for producingcold-spun stainless steel articles, in i the absence of intermediate anneal. Unfortunately, the substantial alteration in composition required to give good spinning properties results in certain undesirable changes in other properties. And, of even greater consequence, all at greatly increased cost.

Accordingly, an important object of our invention is to avoid, in large measure, the several disadvantages heretofore confronting the art, and provide cold-spun austenitic chromium-nickel stainless steel articles, with appreciably reduced manufacturing time, and this through the use of simple operational techniques, in certain and predictable manner, with minimum investment of plant and labor, all in the substantial absence of intermediate anneal and with minimum wear on the forming equipment.

Referring to the practice of our invention, we have found that by the addition of copper to the alloy a much more elfective and important lowering in the rate of workhardening is achieved than is true with increase in either nickel or manganese contents. We find thatwe can subject the resulting metal to considerable cold-spinning without appreciable wear on the forming apparatus, and in the substantial absence of intermediate anneal, all while maintaining within practical and reduced limits both the rate ofwork-hardenin g and the ultimate compression and Starting with an austenitic chrome-nickel stainless steel, 2

then, to which an appreciable amount of copper isadded, we find that a broad range of composition well-suited for the production of cold-spun articles, according to the practice .of our invention, is carbon up to .15%, manganese up to 15%, chromium 10% to 25%, nickel 7% to 20%, copper 1.0% to 6.0%, and remainder iron.

While the nickel and manganese contents undoubtedly contribute to the cold-workability of the metal, it is the copper, however, which appreciably reduces the workhardening properties, and increases in appreciable manner the extent of cold-spinning which can be resorted to in the absence of anneal. i I

Close response tohighly intricate surface configuration, i. e., variation in radii of curvature, is made possible by our invention. Care should be taken, however, to see that the chromium is not present in too high percentage for, as pointed out hereinbefore, two factors effect the cold-work-hardening rate; one of those is the stability in the lower range alloys of the austenite, which is efiected by both the chromium and the nickel content. The second factor is the production of a solid-solution hardening effect when the nickel is present in substantial amount. In this latter case, upon increase in the chromium present in the alloy, the rate of work-hardening is correspondingly increased, although not necessarily in linear proportion.

A variety of cold-spun austenitic chromium-nickel stainless steel articels may be made according to our invention including,illustratively, the ice-bowl shown in the accompanying drawing. Moreover it is apparent from a consideration of the drawing that widely varied configuration can be given to the surface of the bowl, provided only that the bowl be circular throughout its cross section. The metal can be subjected to considerable cold-spinning operations without appreciable evidence of work-hardening or tendency towards increase in ultimate tensile strength. Only infrequently is necessity encountered for intermediate anneal.

The important practical cold-working advantages attending upon the presence of copper in the articles of our. invention is determined by comparing the ultimate tensile strength of samples of stainless steel wire of varying composition upon being subjected, by cold-drawing, to various reductions. These results are disclosed in Table I.

Table 1 Ult. Tensile Str. (1,000 p. s. i.) after cold-drawing from Heat No. Or Ni Cu annealed condition 18. 85 9. 42 78 120 165 212 246 O5 18. 17 ll. 42 82 117 152 187 212 05 13. 9 12. 77 75 113 150 187 03 13. 1b 13. 56 3, 10 75 95 122 145 152 and this even though the ultimate tensile strength inannealed condition is higher for the 18-11 chromiumnickel alloy than for the 18-9 chromium-nickel alloy. Further increase in the nickel with reduction of chromium, as in the third heat, to a more nearly austenitic metal is accompanied by still further, although slight, reductions in the ultimate tensile strengths. In the fourth heat, the addition of an appreciable amount of copper (3.10%) to an alloy otherwise generally similar to that of heat number 3 is attended by further and marked reduction in ultimate tensilestrength. Since this is one of the criteria of ductility and probable response to cold-spinning operations, it is apparent that the introduction of copper in varying percentages contributes importantly towards improving the cold-spinning characteristics of the metal.

As a preferred embodiment, we find that the following range of composition will give the best results in actual practice: carbon 10% maximum, manganese to 2.00%, chromium 10%to 20%, nickel10% to 15%, copper 2.0% to 5.0%, remainder iron.

It is to be notedthat in the foregoing composition the silicon content may well be retained within the normal composition range; it has no apparent effec'ton the work-hardening properties of the metal. Phosphorus and sulfur are normally maintained in low percentage, that is, not exceeding about 0.04% phosphorus and 0.03%

vsulphur (see Metals Hand-book, 1948 editionQA. S. M.

Cleveland, Ohio, page 563), but where some machining is required either of these may range up to ashigh as 0.40% without appreciable disadvantage, Where desired, selenium in amounts up to 0.40% may'be added. Carbon may be stabilized, where desired, by including columbium or titaniumin the usual amounts, say illustratively, 8 percent C minimum for the one and 4 percent C minimum for the other. Resistance to corrosion may be increased by adding up to 4% molybdenum. We have found, 'as suggested, that none of these elements significantly or adversely afiects the cold work-hardening rate of the alloy. l

Thus in accordance with the practice of our invention we produce cold-spun articles in ready manner, and with minimum manufacturing steps. Plant investment is maintained low, and the forming equipment is not only initially simple and of comparatively low first"cost,"but is-of long useful life. Semi-skilled labor is found highly effective in the practice of our invention, while the variety of articles Which may be cold-spun according to our new practice is large. Not only maybe included, the ice-bowl such as disclosed in the drawing, but as well, a variety of hollow-ware articles such as pots and pans, containers and cans, the headsof'chemical tanks, and" generally similar equipment for the household, for commerce, and for industryf Seldom is intermediate anneal required, and the number of anneals is small in those few instances where drastic reductions are employed and annealing resorted to. We find that the inclusion of copper is most effective in lowering the work-hardening rate. The percentage of rejects in manufactureis appreciably reduced. All these, as well as many other practical advantages attend upon the practice of our invention. 7 i

It is apparent from the foregoing that once the broad aspects of our invention are disclosed, many embodiments thereof will readily suggest themselves to those skilled in the art, all falling within the ambit of our disclosure. Accordingly, we intend the foregoing'disclosure to be considered solely by way of illustration, and in no sense as a limitation.

We claim as our invention:

l. Cold-spun and machined articles having the approximate analysis, carbon up to about 0.15%, manganese incidental amounts up to about 15%, from about 10% to about 25% chromium, about 7% to about 20% nickel, about 1.0% to about 6.0% 'copper, one element of the group consisting of about 0.04% to 0.40% phosphorus and about 0.03%to 0.40% sulfur, and remainder lI'OIl.

2. Cold-spun and machined non-magnetic stainless steel articles of manufacture, having the approximate analysis, up to 0.10 carbon, about 0.50% to about 2.00% 5 manganese, about 10% to about 20% chromium, about 10% to about 15% nickel, about 2.0% to about 5.0% copper, one element of the group consisting of about 0.04% to 0.40% phosphorus and about 0.03% to 0.40% sulfur, and remainder iron. 10

References Cited in the file of this patent UNITED STATES PATENTS 2,523,000 Defranoux Sept/19, 1950 15 6 FOREIGN PATENTS 437,592 Great Britain Oct. 23, 1935 OTHER REFERENCES Pub. in 1940 by the McGraw-Hill Book Co., New York. 

1. COLD-SPUN AND MACHINED ARTICLES HAVING THE APPROXIMATE ANALYSIS, CARBON UP TO ABOUT 0.15%, MANGANESE INCIDENTAL AMOUNTS UP TO ABOUT 15%, FROM ABOUT 10% TO ABOUT 25% CHROMIUM, ABOUT 7% TO ABOUT 20% NICKEL, ABOUT 1.0% TO ABOUT 6.0% COPPER, ONE ELEMENT OF THE GROUP CONSISTING OF ABOUT 0.04% TO 0.40 PHOSPHORUS AND ABOUT 0.03% TO 0.40% SULFUR, AND REMAINDER IRON. 